The present invention relates to a display device for an electronic apparatus comprising a solar cell, for example, an electronic apparatus such as a watch, an electronic calculator, a radio, a battery charger, and more particularly the watch.
An example of a conventional structure of a watch having a solar cell 305 will be described in detail with reference to FIG. 26. FIG. 26(a) is a plan view showing the inside of the watch case seen from above and FIG. 26(b) is a schematic sectional view showing the inside of the watch case.
As shown in FIG. 26, when light is incident on a solar display board 301 of a watch from the outside, the light is transmitted through the solar display board 301 to reach the solar cell 305. Then, the solar cell 305 converts an optical energy into an electric energy which is charged into a battery or capacitor referred to as a secondary battery which is provided in a module 307 and can store electricity. The module 307 includes a drive mechanism for the watch so that a minute hand 310 and an hour hand 309 which are fixed to a central shaft 308 are moved thereby. In this case, the solar display board 301 is positioned between the minute hand 310 and hour hand 309 and the solar cell 305.
In recent years, the power generation efficiency of the solar cell has been enhanced, the power consumption of a module has been reduced, and furthermore, battery performance has been improved. Consequently, even if the external shape of a solar cell is much smaller than ever, a minute hand and an hour hand can be driven.
On the other hand, the degree of freedom has been increased for the external shape of a watch case depending on the diversification of the design of the watch. A middle frame 306 is positioned on the outside of the solar cell 305 and the module 307 so that the degree of freedom can be enhanced in respect of the design of the external shape of the watch.
As shown in FIGS. 26(a) and (b), the solar cell 305 and the module 307 are fixed through the middle frame 306 to an outer case which is not shown. Moreover, the minute hand 310 and the hour hand 309 are bonded to the central shaft 308 which extends from the module 307 and are rotated through a driving force applied from the module 307. Furthermore, the solar display board 301 is provided to cover the solar cell 305 and the middle frame 306.
The middle frame 306 is provided with a hook mechanism in order to fix the module 307 to which the solar cell 305 is fastened, which is not shown. When the module 307 is fitted in the middle frame 306, the solar cell 305 and the module 307 are fixed to the middle frame 306 and are accommodated in the outer case and thus fixed therein.
The solar cell 305 has two kinds of substrates, that is, substrates formed of a glass and a resin. For both of them, the solar cell itself has a small thickness. Furthermore, there is a possibility that the substrate formed of a glass might be chipped through a stress such as a shock during or after assembly. The substrate formed of a resin might be deformed by a stress thereof during bonding. For a method of fixation to the watch case, therefore, the solar cell 305 and the middle frame 306 are not fixed but the module 307 and the middle frame 306 are fixed. In the case of the substrate formed of a resin, a metal plate may be provided on the lower face of the solar cell 305 in order to enhance the reliability of rigidity and electrical connection.
Furthermore, in the case in which the solar display board 301 comes in contact with the solar cell 305, the power generation efficiency of the solar cell 305 might be reduced due to a flaw or the like. Therefore, the middle frame 306 also has the function of preventing the reduction of the power generation. When the solar display board 301 is superposed on the solar cell 305, the middle frame 306 protrudes slightly upward from the upper face of the solar cell 305 such that the middle frame 306 comes in contact with the solar display board 301 earlier than the solar cell 305.
Moreover, in the case in which the module 307 having the solar cell 305 fixed thereto is to be incorporated into the middle frame 306, the incorporation can easily be carried out efficiently and productivity can be enhanced if the external shape of the solar cell 305 is coincident with that of the module 307 as shown. As described above in detail, the middle frame is a member which plays an important role in watch construction.
As shown in FIG. 26(a), a boundary line 303 between the solar cell 305 and the middle frame 306 usually requires a clearance for watch assembling work and the clearance is seen to be black through the solar display board 301. Moreover, a plastic material is often used for the middle frame 306 in consideration of easiness of molding, cost, shock absorption and the like. The middle frame 306 is manufactured by injection molding to correspond to the shape of various outer cases. Therefore, a gate track 304 is formed on an upper face of the middle frame 306 due to the injection molding and the gate track 304 is also seen through the solar display board 301. Furthermore, in the case in which a solar cell is divided into some elements to maintain a predetermined voltage and current, a refractive index of light is varied depending on a difference in a material between a cell portion and a dividing line portion and a solar cell element dividing line 302 is also seen through the solar display board 301.
According to the knowledge of the present inventors, such a phenomenon remarkably presents itself when the solar display board 301 is black or blue. FIG. 26 shows an example in which the solar cell element dividing line 302 has a cross-shape and the boundary line 303 between the solar cell 305 and the middle frame 306 has the shape of a black ring on the boundary between a slant line portion and a dotted portion.
For a technique for seeing such a solar cell element dividing line with difficulty, a method disclosed in Japanese Patent Publication No. Hei 5-38464 has conventionally been proposed.
In the Japanese Patent Publication No. Hei 5-38464, only a color diffusing board is provided between the solar display board 301 and the solar cell 305. However, the diffusing board has the function of diffusing light. Therefore, the boundary line 303 between the solar cell 305 and the middle frame 306, the gate track 304 generated through the injection molding of the middle frame, and furthermore, the solar cell element dividing line 302 are seen with difficulty. As a result, they are necessarily seen to be white so that the tone of the solar display board 301 provided thereabove is affected.
According to an experiment carried out by the present inventors, if only the color diffusing board is provided between the solar display board 301 and the solar cell 305, a black solar display board is seen to be gray, which is not preferable in respect of design. Moreover, a white solar display board has diffusion effects by itself. Therefore, even if the diffusing board is not used, there is not such a phenomenon that the boundary line 303 between the solar cell 305 and the middle frame 306, the gate track 304 generated through the injection molding of the middle frame 306, and furthermore, the solar cell element dividing line 302 are seen through the solar display board 301. Therefore, it is not necessary to provide the diffusing board as in the Japanese Patent Publication No. Hei 5-38464.
Usually, various designs are given through the solar display board 301. If there is such a phenomenon that the boundary line 303, the gate track 304 and the solar cell element dividing line 302 are seen as described above, the quality of design of a watch is adversely affected. More specifically, in this case, a decoration or the like should be given to a part of the solar display board 301 or the whole surface thereof in order to hide the above-mentioned phenomenon. Therefore, the design for the solar display board 301 is restricted so that a feeling of high quality for a watch is eliminated.
In the three phenomena adversely affecting the design quality as described above, the solar cell element dividing line 302 can be considerably improved by giving a protective coat formed of an epoxy resin which has SiO2 particulates distributed therein over the whole surface of the solar cell 305. Moreover, there is a possibility that the gate track 304 generated during the injection molding of the middle frame 306 can also be improved by changing a gate position. However, the boundary line 303 between the solar cell 305 and the middle frame 306, that is, the clearance cannot be avoided for the watch assembling work and is the most harmful and measures are taken with difficulty.
In the experiment carried out by the present inventors, the colors of black and blue solar display boards are caused to be deeper, a feeling of high quality can be obtained for goods by the deeper colors, and furthermore, it is possible to eliminate such a drawback that the observation through the solar display board described above is caused. However, transmitted light does not fully reach the solar cell itself so that the power generation efficiency is reduced and the operation of the watch is stopped.
Moreover, when the tone of the middle frame is adapted to that of the solar cell, it is possible to eliminate such a drawback that the observation through the solar display board described above is caused. However, the boundary line between the solar cell and the middle frame is seen so that the drawback cannot be eliminated completely. Furthermore, when a white paint is thinly applied to the solar cell side of the blue solar display board having a blue resin kneaded therein, it is possible to eliminate such a phenomenon that the boundary line 303 between the solar cell 305 and the middle frame 306, the gate track 304 generated through the injection molding of the middle frame 306, and furthermore, the solar cell element dividing line 302 are seen through the solar display board 301. However, the depth of the color of the solar display board 301 is eliminated by the diffusing function of the white paint so that the feeling of high quality for the single solar display board disappears. In otherwords, the formation of a diffusion layer cannot obtain sufficient effects.
In a display board such as a watch dial, various coloring and patterns are applied to the surface or back of the display board or both of them in order to give a feeling of high quality (added value) in some cases. The coloring is carried out by printing the surface of a material to be the display board or manufacturing the display board from a resin containing a pigment, for example. In the case of a metallic display board, moreover, the pattern on the surface thereof is formed through etching, a matte processing or the like. In the case of a display board formed of a resin, a pattern is formed by injection molding the resin in a mold having the pattern formed therein.
However, the above-mentioned display boards are not satisfactory in respect of the depth of a pattern, a three-dimensional effect and the like.
In consideration of such circumstances, it is an object of the present invention to provide a display device for an electronic apparatus comprising a solar cell and a middle frame for fixing the solar cell and a module to an outer case in which necessary and sufficient light can be caused to reach the solar cell, a feeling of high quality can be given, and furthermore, it is possible to increase a variation in design in which a decorative property is great and the depth of a pattern and a three-dimensional effect are excellent.
The present invention solves the problems of the conventional art described above by providing a display device for an electronic apparatus comprising a solar cell, wherein a circular polarizing plate for transmitting light is provided on the front side of the solar cell in a direction of incidence of light.
In a circular polarizing plate constituted by a linear polarizing plate and a phase difference plate, the linear polarizing plate and the phase difference plate are provided in this order in a direction of incidence of light. Consequently, light reflected by a solar cell surface can be blocked, a boundary line between the solar cell and the middle frame, a gate track generated through injection molding of the middle frame, and a solar cell element dividing line cannot be seen through the circular polarizing plate.
Consequently, the tone of the solar display board is not affected. Moreover, it is not necessary to hide the three drawbacks through a stripe-shaped pattern or the like. Thus, a variation in design of the solar display board can be increased. Furthermore, a solar display board having a deep color can be used so that a feeling of high quality can visually be obtained as goods. By directly giving marking such as a numeral to the linear polarizing plate by means of printing or the like, the function of the solar display board can also be given to the linear polarizing plate itself.
Moreover, the present invention is characterized in that the surface of the circular polarizing plate is provided with a solar display board constituted by a resin substrate having a pattern, an in organic substrate having a pattern or a decorating thin film member or a combination thereof.
Therefore, a decorative property is great, the pattern becomes rich and an excellent three-dimensional effect can be obtained. Through a combination of two or more patterns or two or more materials, moreover, it is possible to manufacture a display board having a better feeling of beauty than ever. Thus, a design variation can be increased.
By such a structure, it is possible to provide a display device for an electronic apparatus comprising a solar cell capable of maintaining the necessary and sufficient power generation efficiency of the solar cell, giving a feeling of high quality and increasing a variation in design.